Power Converter Neutral Wire Fault Detection Using Phase Voltage Imbalance
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Solution Overview
Problem
Existing power converters struggle to accurately distinguish between a sampling loop fault and a missed or disconnected neutral wire in three-phase alternating current power grids, leading to low accuracy in neutral wire fault detection.
Innovation Solution
A power converter with current imbalance branches formed by capacitors, resistors, and inductors between phase wires and the neutral wire, allowing for the detection of voltage deviations to determine neutral wire connectivity issues, and a control circuit to calculate phase voltage differences to identify faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current detection method is used to detect neutral wire faults, then the detection process is simple, but the detection accuracy is low and cannot distinguish between sampling loop faults and neutral wire disconnection faults
Solution Approach 1:
The patent introduces current imbalance branches as intermediary elements connected between the neutral wire and phase wires. These branches contain current detectors that indirectly measure neutral wire status by detecting current imbalances, rather than directly detecting the neutral wire connection status. This intermediary approach enables accurate fault differentiation while maintaining system simplicity.
Solution Approach 2:
The system implements feedback by continuously monitoring current values in the current imbalance branches and comparing them against expected ranges. When current imbalances exceed thresholds, the system generates fault signals to differentiate between sampling loop faults and neutral wire disconnection faults, providing accurate real-time feedback on neutral wire status.
2Measurement precision
If current imbalance branches with capacitors, resistors, and inductors are added to enable accurate neutral wire fault detection, then detection accuracy improves, but device complexity increases
Solution Approach 1:
The patent merges the detection functionality into existing circuit structures by integrating current imbalance branches with the power conversion circuit. The current detectors are incorporated within the control circuit, and the branches utilize standard electrical components (capacitors, resistors, inductors) that can be integrated into existing power electronics designs, reducing overall system complexity despite added detection capabilities.
Solution Approach 2:
The current imbalance branches serve multiple functions: they detect neutral wire disconnection faults, differentiate between sampling loop faults and neutral wire faults, and provide continuous monitoring of neutral wire status. This multi-functionality justifies the added circuit complexity by providing comprehensive fault detection and differentiation capabilities in a single integrated system.
Data Source
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AI summary
This application provides a power converter and a detection method thereof. The power converter includes a power conversion circuit and a control circuit. Three branches are formed between three phase wires of the power conversion circuit and an N wire, and the three branches form current imbalance branches. The power conversion circuit includes an inverter circuit and a filter circuit, and the three branches are located behind the filter circuit. When the N wire is normally connected, a voltage of the N wire does not deviate from a center point when clamped by a voltage of a power grid. Therefore, differences between every two of three phase voltages are less than a specified threshold. When the control circuit determines that the differences are less than the specified threshold, it is considered that the N wire is normal, and the inverter circuit can be started or run normally. When the N wire is faulty, a voltage of the N wire deviates from a center point due to the current imbalance branches. Therefore, differences between every two of the three phase voltages are greater than a specified threshold. When the control circuit determines that a difference is greater than the specified threshold, it is considered that the N wire is abnormally connected, and an N-wire fault alarm signal is output.